Sewing machine bobbin preheater attachments



Feb. 28, 1956 M. ROBERTS ET AL 2,736,280

SEWING MACHINE BOBBIN PREHEATER ATTACHMENTS Filed Feb. 23, 1955 2 Sheets-Sheet 1 i lnvenzors 111 New rice IPaberzs F6 GordorzC JI l akef'lleld Feb. 28, 1956 M, ROBERTS ET AL 2,736,280

SEWING MACHINE BOBBIN PREHEATER ATTACHMENTS Filed Feb. 25, 1955 2 Sheets-Sheet 2 1 m x w Inventors Jfiurz'ce Roberts Gordon 0 J VI/akefZEZd United States Patent SEWING MACHINE BOBBIN PREHEATER ATTACHMENTS Maurice Roberts and Gordon ,Cecil John Wakefield, Leicester, England, assignors to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application February 23, 1955, Serial N 0. 490,102

Claims priority, application Great Britain March 4, 1954 7 Claims. (Cl. 112-41 This invention relates to improvements in attachments for preheating sewing machine bobbins and bobbin cases. An illustrative attachment comprises a heated combination holder for a bobbin and its case suitable for use with a curved hook needle lockstitch sewing machine intended for use in sewing shoe outsoles. A type of machine for this purpose is disclosed in United States Letters Patent No. 2,056,670, granted October 6, 1936, upon application of Gouldbourn et 211.

It is the usual practice in the manufacture of shoes to sew the outsole with wax thread and machines for this purpose are provided with a curved hook needle and a shuttle containing a supply of locking thread provided by a bobbin contained within a bobbin case. In order to condition the wax thread on a bobbin and to render it sufficiently flexible for sewing, the shuttle is heated by an electric cartridge and the bobbin thread is subjected to heat transferred by conduction and radiation from the shuttle. The wax thread must not be heated to too high a temperature or it becomes charred. If it is too cool it is insufiiciently flexible for effective sewing. In order to avoid delay when it is necessary to replace an empty bobbin by a newly filled one, it is customary also to preheat the filled one before it is inserted in the shuttle.

To replace an empty bobbin, in the machine of the patent referred to, it is necessary to remove the bobbin case and to eject the empty bobbin therefrom, both case and bobbin being heated ordinarily within a range of from 125 to 150 B, so that there exists a troublesome problem of handling the bobbin and case without burning the fingers or at least suffering some discomfort from the heat of the parts. Besides ejecting the empty bobbin it is necessary to pass thread from a newly filled preheated bobbin through a slot in the side wall of the bobbin case, to apply the filled bobbin to the bobbin case, to draw the thread end under a tension spring on the bobbin case, to pass the thread through a guiding staple fixed to the bobbin case, and to return the refiilled bobbin case into the sewing machine shuttle, all of these operations subjecting the operator to further discomforture or likelihood of burns. To avoid burns the operator commonly wraps a bobbin case after removal from the shuttle in a rag and while held in the rag the necessary replacement and rethreading is accomplished. Holding the bobbin case in a rag is insecure and the rag may interfere with the threading operation. In any event, the replacement and rethreading necessitate a delay which enables the bobbin and case to become cooled somewhat below their most effective temperature, so that in spite of preheating the bobbin the first few stitches of a seam after replacement may not be inserted in the most desirable manner as a result of lack of flexibility of the thread.

An object of the present invention is to provide convenient means by which it is possible to reduce the time required to replace an empty bobbin and to rethread the bobbin case with a newly filled bobbin heated to a temperature within the limits of the range specified for a machine of the type referred to, thereby improving the ice first few stitches of a new seam inserted after replacement has been made. A further object is to provide a convenient support for heating both the bobbin and bobbin case of a sewing machine during at least a part of the time required to replace an empty bobbin with a filled one, so that large degree variations of temperature in the locking thread during sewing are avoided.

With these and other objects in view, the illustrated attachment is provided with a pair of adjacent holders shaped to fit a bobbin and a case from which it is separated, the case being cylindrical with a closed end and being formed with external thread engaging and controlling devices along a limited section of its cylindrical wall and with a projection on its closed end, the bobbin case holder being cup shaped with an opening in its side wall to expose the thread engaging devices with which the bobbin case is equipped and having means arranged to fit the projection on the closed end of the bobbin case for preventing insertion of the case in its holder at any angular relationship therewith except one in which the thread engaging devices are exposed in the opening of the holder side wall. In the form of this feature hereinafter described, the projection on the thread case is tongue-shaped with an undercut recess beneath it and the means on the bobbin case holder for retaining the case at the proper angular relationship includes a second projection overlapping the projection on the bobbin case and entering the recess in the bobbin case.

These and other features of the invention, as hereinafter described and claimed, will become apparent from the following detailed specification taken in connection with the accompanying drawings, in which:

Fig. l is a perspective view of a preheater attachment embodying the features of the invention, looking from a position above the front and left side with a bobbin and bobbin case shown in preheating position therein;

Fig. 2 is a view looking in the direction of the arrow II of Fig. 1 and showing the preheater attachment with the bobbin and case removed;

Fig. 3 is a view in sectional side elevation of the attachment, taken along the line IlI-III of Fig. 2, including the bobbin and its case; and

Fig. 4 is a view of the closed end of a bobbin case which fits within the preheater attachment.

The preheater attachment shown in the drawings is permanently mounted on a curved hook needle, shoe outsole, lockstitch sewing machine and has a hollow base 2 secured at a location close to and beneath the shuttle which is similar to that disclosed in the Gouldbourn et a1. patent, above identified. To secure the base 2 to the machine the sides of the base have threaded openings entering their edges within which are engaged screws 4 (see Fig. 3) passing through a work bench 6 carried by the frame of the machine. The attachment is provided with a pair of separated heated holders shaped to fit a bobbin and bobbin case.

The bobbin holder is shown at 3 and is cup shaped to accommodate the bobbin. The holder 8 has passing through the center of its bottom end wall a hollow stud 19 (Fig. 3), which also passes through an electrical heat-' ing element in the form of a disk 12 engaging the bottom of the holder 8. To secure the holder and disk to the body portion of the attachment the lower end of the stud 10 is threaded and is engaged by a nut 14 which clamps the stud in a boss on the base 2. A midportion of the stud has a collar 16 fitting a counterbore in the end wall of the holder. Above the collar 16 the stud is of reduced diameter and forms a hollow spindle of a diameter to fit within the ferrule of a bobbin, indicated at 18, the outer wall of the cup shaped holder surrounding the bobbin and serving to transmit heat derived from the heating element by radiation to the thread on the bobbin. The spindle is of sufficient length to support two or three additional bob= bins if required, although the outer wall of the holder 8 is capable of enclosing one bobbin only at a time. To facilitate removal of a preheated bobbin from the spindle, the outer side wall of the holder has two openings 25) disposed approximately 180 apart and arranged to enable the finger and thumb of the machine operator to grasp the upper flange of the bobbin without touching the heated holder.

The case within which the bobbin is introduced before being inserted in the shuttle of the machine is illustrated at 22 in Fig. 4. The bobbin case is cylindrical with one closed end and is formed with external thread engaging and controlling devices along a limited section of its cylindrical side wall. At its closed end the case has a tongue shaped projection 24 (see also Fig. 3) and a radial edge face 26 forming an undercut recess 23 between the projection and the closed end of the case. The closed end of the bobbin case also has a V-shaped projection 30 forming an edge face 32. To control the thread running from a bobbin in the bobbin case the end, indicated at 34, of the thread is guided by the thread engaging devices on the case, comprising a thread receiving slot 36 (see Fig. 1) extending through the cylindrical side wall of the bobbin case, a thread tension spring 38 in a groove formed in the side wall of the bobbin case and a thread guiding staple 49 (see Fig. 4) on the side wall of the case.

The holders for the bobbin and case are separated but are sufiiciently close together that the thread may be carried from the bobbin through the thread engaging devices on the case without exposing an excessively long portion of its length to cooling action of the surrounding air. After the thread has been passed through the guiding slot 36 the preheated bobbin in the holder 8 is removed from the spindle portion of the stud 1t) and is introduced within the bobbin case. its ferrule portion fits a tubular projection 42 (Fig. 3) in the thread case. The remaining threading operations are then completed.

The bobbin case holder comprises a cup shaped pocket 43 formed with an opening in its side wall through which the bobbin case may be inserted or removed. The pocket is disposed on the base 2 at a position where the thread end 34. may be passed from a bobbin on the attachment through the slot 36 in the bobbin case beneath the tension spring 38 and through the staple 4% without removing the bobbin or case from their holders. The base about the pocket has an inner semicircular face 44 formed to surround approximately one-half of the periphery of the bobbin case, and a flat web 46 disposed at right angles to the face 44 engages the closed end of the bobbin case. When the bobbin case 22 is inserted in the pocket 43 the outer surfaces of the end wall on the case fit snugly with corresponding surfaces of the web 46. The side wall of the bobbin case fits closely within its holder without actually contacting the face 44 and a flange 48 projecting inwardly from the semicircular face 44 overlies the upper edge of the bobbin case side wall. The upper edge of the web as hasv a beveled projection 50 about which the projection 24 on the thread case is overlapped, the web projection 5 entering the undercut recess 28 above the projection 24.

To assist in inserting the bobbin case in its pocket in the proper angular relationship with the thread engaging devices exposed in the opening of the pocket, the holder web 46 has a straight edge 52 (see Fig. 2) which engages the face 26 on the bobbin case to limit its angular movement in one direction and the holder web has a straight edge 54 which engages the bobbin case face 32 to limit its angular movement in the other direction. The faces 26 and 32 on the bobbin case are located at opposite sides of the center of the bobbin case so that the angular relation of the bobbin case with the holder is definitely determined by the engagement therewith of these faces, the bobbin case projection 3i) entering an opening formed by the straight edge 54 of the pocket; Also, the bevel of the projection 50 terminates at-twosides of the bobbincase iii projection 24 along lines 56, which confine the projection on the bobbin case still further and provide additional means for limiting the angular relation between the bobbin case and its holder.

To heat the bobbin and case holders there are attached to them heating and heat controlling elements including the heating disk 12. The other heating element is on the bobbin case holder and consists of a separate electrical heating disk 60 secured to the lower surface of the case holder by means of a bolt 58. The heat controlling element is housed within the hollow stud 18 of the bobbin holder only and comprises a thermostat bulb 62, acting in a well-known manner through a metal bellows (not shown) to open or close a circuit comprising wires 64 running through the heating disks. To enclose the forward side of the hollow base 2 and to retain the heat therein a detachable guard plate 66 is fixed to the outer walls of the base below the heating disk 60.

To increase the convenience with which the bobbin case 22 is inserted and retained in proper angular relationship within the pocket of its holder the plane of the case holder defined by the web 46 is inclined downwardly, looking from the front of the machine, in a direction corresponding to that in which the projection on the holder for the bobbin case enters the undercut recess 23 in the case. The opening in the pocket is uppermost and is of sufiicient width to admit the bobbin case after the end wall of the case first engages the fiat web 46 of the holder, so that during continued movement of the case through the opening into the holder pocket the case slides along the surface of the web 46. During the sliding movement of the bobbin case along the web of the case holder and the entry of the projection 56 on the web into the undercut recess 28 on the bobbin case, the bobbin case is oriented and brought into proper angular relationship with respect to the case holder. By reason of the incline of the case holder plane the bobbin case is retained in the holder pocket under the influence of gravity, the faces 52 and 54 serving to position with accuracy and to restrain the bobbin case against displacement from angular relationship with the case holder. The projection S ll within the recess 28 of the bobbin case serves to restrain the bobbin case against displacement axially from its holder.

In operation of the preheater a newly filled bobbin is applied to the bobbin holder 3 after the end 34 of the thread has been disengaged. As soon as the machine on which the preheater is mounted has consumed all of the thread on a bobbin, the operator of the machine removes the bobbin case from the machine tipping the case to enable the empty bobbin to drop therefrom onto the shelf 6. The case is quickly reinserted into the holder minimizing the danger of burns. The end 34 of the thread is then passed through the slot 36, drawn beneath the tension spring 38 and carried through the staple 4th. The preheated bobbin is removed from the spindle of the stud 19 and inserted in the bobbin case where it is ready to be lifted conveniently and applied to the shuttle in the sewing machine. Alternatively the bobbin may be inserted in the bobbin case as soon as the end of the thread is passed through the slot 36, the remaining threading operations being completed before the bobbin case is removed from the holder.

If the operators hands are sensitive to heat the protection of a cloth or piece of leather may be taken advantage of without rendering the use of the preheating attachment awkward or cumbersome. The convenience and close relationship of the holders for the bobbin and case in the attachment, as well as the security with which the bobbin case is held lend themselves however to such efiective handling of the bobbin case that after brief practice burns are usually entirely avoided.

The nature and scope of the invention having been indicated and an embodiment having been described, what is claimed is:

l. A bobbin and bobbin case preheater for mounting on a sewing machine, said preheater comprising a pair of separated heated holders shaped to accommodate a bobbin and a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical wall and a projection on its closed end, said holders being sufiiciently close together to enable thread to be carried from the bobbin through the thread engaging devices on the bobbin case without cooling the thread excessively, and the bobbin case holder being cup shaped with an opening in its side wall through which the bobbin case may be inserted, in combination with means on the bobbin case holder fitting the projection on the closed end of the bobbin case for retaining the case in its holder at an angular relationship with the holder, in which the thread engaging devices are exposed in the opening of the holder side wall.

2. A bobbin and bobbin case preheater for mounting on a sewing machine, said preheater comprising a pair of separated heated holders shaped to accommodate a bobbin and a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical wall and a tongue shaped projection with an undercut recess, said holders being sufficiently close together to enable thread to be carried from the bobbin through the thread engaging devices on the bobbin case, without cooling the thread excessively, and the bobbin case holder being provided with an opening in its side wall through which the bobbin case may be inserted, in combination with a projection on the bobbin case holder about which the projection on the bobbin case is overlapped to cause the projection on its holder to enter the recess in the bobbin case for retaining the bobbin case in its holder at an angular relationship therewith, in which the thread engaging devices are exposed in the opening of the case holder side wall.

3. A bobbin and bobbin case preheater for mounting on a sewing machine, said preheater comprising a pair of separated holders shaped to accommodate a bobbin and a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical wall and a projection on its closed end, said holders being suificiently close together to enable thread to be carried from the bobbin through the thread engaging devices on the bobbin case without cooling the thread excessively, and the bobbin case holder being cup shaped with an opening in its side wall through which the bobbin case may be inserted, in combination with means on the bobbin case holder fitting the projection on the closed end of the bobbin case for retaining the case in its holder at an angular relationship with the holder, in which the thread engaging devices are exposed in the opening of the holder side wall, and heating and heat controlling elements on the holders, one of the heating elemerits being attached to the bobbin case holder, including a thermostat within the bobbin holder only.

4. A bobbin and bobbin case preheater for mounting on a sewing machine, said preheater comprising a pair of separated heated holders shaped to accommodate a bobbin and a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical wall and a projection on its closed end, said holders being sufiiciently close together to enable thread to be carried from the bobbin through the thread engaging devices on the bobbin case without cooling the thread excessively, and the bobbin case holder being cup shaped with an opening in its side wall through which the bobbin case may be inserted, in combination with means on the bobbin case holder fitting the projection on the closed end of the bobbin case for retaining the case in its holder at an angular relationship with the holder, in which the thread engaging devices are exposed in the opening of the holder side wall, and heating and heat controlling elements on the holders, including a hollow spindle of a diameter to fit within a bobbin in the bobbin holder and a thermostat within the spindle.

5. A bobbin and bobbin case preheater for mounting on a sewing machine, said preheater comprising a pair of separated heated holders shaped to accommodate a bobbin and a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical wall and a projection on its closed end, said holders being sufiiciently close together to enable thread to be carried from the bobbin through the thread engaging devices on the bobbin case without cooling the thread excessively, and the bobbin case holder being cup shaped with an opening in its side wall through which the bobbin case may be inserted, in combination with means on the bobbin case holder fitting the projection on the closed end of the bobbin case for retaining the case in its holder at an angular relationship with the holder, in which the thread engaging devices are exposed in the opening of the holder side wall, and heating and heat controlling elements on the holders, includ ing a hollow spindle of a diameter to fit within a bobbin in the bobbin holder and a thermostat within the spindle, said spindle being of sufficient length to support additional bobbins thereon.

6. A bobbin and bobbin case preheater for mounting on a sewing machine, said preheater comprising a pair of separated heated holders shaped to accommodate a bobbin and a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical wall and a tongue shaped projection with an undercut recess, said holders being sufficiently close together to enable thread to be carried from the bobbin through the thread engaging devices on the bobbin case without cooling the thread excessively, and the bobbin case holder being provided with an opening in its side wall through which the bobbin case may be inserted, in combination with a projection on the bobbin case holder about which the projection on the bobbin case is overlapped to cause the projection on its holder to enter the recess in the bobbin case for retaining the bobbin case in its holder at an angular relationship therewith, in which the thread engaging devices are exposed in the opening of the case holder side wall, the plane of the bobbin case holder being inclined downwardly in a direction corresponding to that in which the projection on the holder for the bobbin case enters the recess in the bobbin case to retain the case in its holder under the influence of gravity and to restrain the case from displacement.

7. A bobbin case preheater for mounting on a sewing machine, said preheater comprising a heated holder shaped to accommodate a cylindrical closed ended bobbin case formed with external thread engaging devices along a limited section of its cylindrical side wall, and a tongue shaped projection with an undercut recess, the bobbin case holder being provided with an opening in its side wall through which the bobbin case may be inserted, in combination with a projection on the bobbin case holder about which the projection on the bobbin case is overlapped to cause the projection on the holder to enter the recess in the bobbin case for retaining the bobbin case in its holder at an angular relationship with the holder in which thread engaging devices are exposed in the opening of the holder side wall, the plane of the holder being inclined downwardly in a direction corresponding to that in which the projection on the holder enters the undercut recess in the bobbin case to retain the bobbin case under the influence of gravity in its holder at an angular relationship with the holder in which the thread engaging devices are exposed in the opening of the holder side wall.

Morneau Nov. 14, 1911 Bates Feb. 3, 1914 

